Initializeable

For issue #24 
I've got my exam this afternoon, but I can't see why this shouldn't work with `super`. I might be overlooking something, but I think this should work:

You should make `Initializable` inherit from `Brick` instead of `object`. (You can use the `ABCMeta` metaclass to force it to be an abstract class if you are afraid of people instantiating it.) You should then no longer inherit from both `Brick` and `Initializable`, but only from `Initializable` (although it's perfectly fine to inherit from both `Initializable` and another subclass from `Brick`). Lastly, make sure that `Initializable` calls `super(Initializable, self)._push_initialization_config()` so that we don't have situations where the other derived class's method doesn't get called.